Display Device

ABSTRACT

In a display device having driving circuits formed on the same substrate where pixels are formed, the lateral frame area of the display device is reduced. A gate signal line driving circuit is placed in parallel with a source signal line driving circuit, so that no driving circuits are provided in at least two opposing directions out of four directions with respect to a pixel region. With the above-described structure, the area the gate signal line driving circuit occupies in prior art is removed to reduce the width (side to side) of the display device. Therefore a display device that has a small frame area in the lateral direction can be provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/041,454, filed Jan. 25, 2005, now allowed, which is a continuation ofU.S. application Ser. No. 10/211,294, filed Aug. 5, 2002, now U.S. Pat.No. 6,862,008, which claims the benefit of a foreign priorityapplication filed in Japan as Serial No. 2001-241463 on Aug. 8, 2001,all of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display device in which a pluralityof pixels are formed on an insulating surface and the luminance of thepixels is changed to display an image. Specifically, the presentinvention relates to a display device in which a driving circuit forcontrolling the luminance of pixels is provided on the same insulatingsurface where the pixels are formed.

2. Description of the Related Art

Display devices are incorporated in various electronic equipment.Reduction in size and power consumption is required for display devices,particularly for ones that are used in portable information equipment.

Display devices that are attracting attention for their reduced size andpower consumption are flat panel displays such as liquid crystal displaydevices and OLED display devices using OLED (organic light emittingdiode) elements.

These flat panel displays each have a plurality of pixels that form amatrix pattern on a substrate having an insulating surface. The flatpanel displays form an image by using a driving circuit to selectivelyinput a video signal to one pixel and change the luminance of the pixel.

There are various ways to connect pixels to a driving circuit.

As one way to connect pixels to a driving circuit for controlling theluminance of the pixels, the driving circuit is formed on a separatesubstrate such as a single crystal IC substrate and the substrate isbonded to the top face of a substrate having an insulating surface onwhich the pixels are formed. In this case, a large area is needed tobond the single crystal IC substrate to the substrate having aninsulating surface on which the pixels are formed. In addition, thewiring resistance between the driving circuit and the pixels is large.Therefore it is difficult to provide a display device that is small insize and power consumption.

In another way to connect pixels to a driving circuit, the drivingcircuit is integrally formed on the same insulating surface where thepixels are formed. The driving circuit is composed of a thin filmtransistor (TFT) on the same insulating surface where the pixels areformed. This method can provide a display device that is small in sizeand power consumption.

FIG. 9 shows a top view of a display device having a pixel region inwhich a plurality of pixels form a matrix pattern and driving circuitsthat are formed in the periphery of the pixel region.

A source signal line driving circuit 902, gate signal line drivingcircuits 901 (901A and 901B), and a pixel region 903 are placed on asubstrate 900 having an insulating surface. Signals to be inputted tothe driving circuits (source signal line driving circuit 902 and gatesignal line driving circuits 901) are supplied from an FPC substrate904.

When viewed from above, a region of the display device excluding thepixel region 903 is referred to as frame. In other words, a frame in adisplay device corresponds to a region that does not display an image.

In a liquid crystal display device, the luminance of each pixel isdetermined by controlling the transmittance, which is achieved bycontrolling the orientation of each liquid crystal element. A liquidcrystal element has a liquid crystal material placed between twoelectrodes. One of the electrodes of the liquid crystal element(hereinafter referred to as pixel electrode) is formed on a substrate onwhich a driving circuit and other components are formed (hereinafterreferred to as pixel substrate) and the other electrode of the liquidcrystal element (opposite electrode) is formed on a separate substrate(hereinafter referred to as opposite substrate). The pixel substrate andthe opposite substrate are bonded to each other such that the pixelelectrode faces the opposite electrode.

On the pixel substrate, a seal member is arranged so as to surround thepixel region and the driving circuits and then the opposite substrate isbonded. A liquid crystal material is sealed in the space surrounded bythe pixel substrate, the opposite substrate, and the seal member. Whenthe display device shown in FIG. 9 is a liquid crystal display device,906 is the seal member used to bond the pixel substrate 900 to theopposite substrate. The opposite substrate and the liquid crystalmaterial are not shown in FIG. 9.

In an OLED display device, the luminance of each pixel is determined bycontrolling light emission of each OLED element. An OLED element isformed on a pixel substrate after TFTs constituting a driving circuitand other components are formed. An OLED element is by nature degradedconsiderably by oxygen, moisture, and the like when it is brought intocontact with the outside air. For that reason, the OLED display deviceemploys a structure in which a cover member is placed after an OLEDelement is formed to shut the OLED element off of the outside air. Thecover member is bonded to the top face of the pixel substrate using aseal member.

On the pixel substrate, the seal member is arranged so as to surroundthe pixel region and the driving circuits and then the cover member isbonded. The OLED element is sealed in the space surrounded by the pixelsubstrate, the cover member, and the seal member. When the displaydevice shown in FIG. 9 is an OLED display device, 906 is the sealmember. The cover member is not shown in FIG. 9.

It is common to various display devices including liquid crystal displaydevices and OLED display devices that the pixel region 903 has x (x is anatural number) source signal lines S1 to Sx arranged in parallel withone another and y (y is a natural number) gate signal lines G1 to Gywhich are arranged in parallel with one another and which areperpendicular to the source signal lines S1 to Sx. Through the sourcesignal lines S1 to Sx and gate signal lines G1 to Gy, pixels areselected and the luminance of the pixels selected is controlled.

The source signal line driving circuit 902 inputs signals to the pluralsource signal lines S1 to Sx. The gate signal line driving circuits 901(901A and 901B) input signals to the plural gate signal lines G1 to Gy.The driving circuits 902 and 901 are formed in the periphery of thepixel region 903.

The source signal line driving circuit 902, which is composed of a shiftregister and other components, outputs signals sequentially in ascanning direction indicated by the arrow in the drawing. The signalsoutputted are inputted to the plural source signal lines S1 to Sx.Usually, the source signal line driving circuit 902 is arranged suchthat the scanning direction is perpendicular to the source signal linesS1 to Sx that are arranged in parallel to one another. Similarly, thegate signal line driving circuits 901, which are composed of a shiftregister and other components, output signals sequentially in a scanningdirection indicated by the arrow in the drawing. The signals outputtedare inputted to the plural gate signal lines G1 to Gy. Usually, the gatesignal line driving circuits 901 are arranged such that the scanningdirection is perpendicular to the gate signal lines G1 to Gy that arearranged in parallel to one another.

In FIG. 9, the gate signal line driving circuits 901 (901A and 901B) areformed to the left and right of the pixel region. Alternatively, onlyone side of the pixel region may have a gate signal line drivingcircuit.

The scanning direction of the gate signal line driving circuits 901arranged as described above is called a row direction whereas thescanning direction of the source signal line driving circuit 902 iscalled a column direction.

In FIG. 9, the source signal line driving circuit 902 is formed inparallel to one of four sides of the rectangle of the pixel region 903.The gate signal line driving circuits 901A and 901B are each formed inparallel to one of two sides of the rectangle, which are different fromthe side parallel to the source signal line driving circuit 902 andwhich are not opposed to the source signal line driving circuit 902.

In this specification, of four sides of the pixel region 903 on thepixel substrate 900, the side connected to the FPC substrate 904 iscalled an upper side and the side opposing to the upper side is called alower side.

Of four sides of the pixel region 903 on the pixel substrate 900, oneside that is abutted with the side connected to the FPC substrate 904,and the side opposite to the one side are called a left side and rightside of the pixel region, respectively.

Usually, the place of the source signal line driving circuit 902 is theclosest to the area where the FPC substrate is bonded. Therefore thesource signal line driving circuit 902 is generally placed above thepixel region 903. On the other hand, the gate signal line drivingcircuits 901 are placed to the left and right of the pixel region 903 onthe pixel substrate 900.

Out of the four sides of the pixel region 903 on the pixel substrate900, the source signal line driving circuit 902 may be placed on theside opposite to the side where the FPC substrate 904 is connected. Inthis case, the place of the source signal line driving circuit is belowthe pixel region.

It is assumed that above, below, left, and right of the pixel region 903correspond to above, below, left, and right of the display device,respectively.

Users of portable information equipment such as cellular phones demandas large a screen as possible for displaying an image and reduction inwidth of equipment body so that it is easy to hold.

In order to obtain as large a display screen as possible and reduce thewidth of equipment body as much as possible, the area of the frame of adisplay device incorporated in the equipment body has to be reduced.

In the display device structured as shown in FIG. 9, the gate signalline driving circuits 901A and 901B are placed to the left and right ofthe pixel region 903.

Furthermore, the seal member 906 is formed on the outside of the gatesignal line driving circuits 901A and 901B on the pixel substrate 900.Accordingly, the area of the frame on the left and right of the displaydevice cannot be reduced.

Also, the area of the frame can be reduced only to a limited degree onthe upper and lower sides of the pixel region since the FPC substrate isconnected.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above, and an objectof the present invention is therefore to provide a display device whichhas driving circuits for supplying signals to a plurality of pixels onthe same insulating surface where the plural pixels are formed and whichhas reduced frame area on its left and right sides.

The present invention provides a display device with driving circuitsfor supplying signals to a plurality of pixels being formed on the sameinsulating surface where the plural pixels are formed in which a firstdriving circuit (gate signal line driving circuit) is in parallel with asecond driving circuit (source signal line driving circuit). In thisway, no driving circuits are placed in at least two opposing directionsout of four directions with respect to a pixel region, thereby obtaininga display device with the frame area reduced on its left and rightsides.

Here, to place a gate signal line driving circuit and a source signalline driving circuit in parallel to each other means that the scanningdirection of the gate signal line is in parallel to the scanningdirection of the source signal line driving circuit.

In this specification, a scanning direction of a driving circuit meansthe direction of aligning circuits each associated with one of pluralsignal lines to which signals are inputted from the driving circuit.

In general, it is desirable if signals outputted from a source signalline driving circuit are inputted to a pixel region through as short adistance as possible. Accordingly, when a source signal line drivingcircuit and a gate signal line driving circuit are formed on the sameside of a pixel region, the source signal line driving circuit isarranged so as to be closer to the pixel region than the gate signalline driving circuit.

It is also possible to place the gate signal line driving circuit nearerto the pixel region than the source signal line driving circuit.

Alternatively, the source signal line driving circuit is placed onlyabove or below the pixel region whereas the gate signal line drivingcircuit is placed only on a side of the pixel region which is oppositeto the side where the source signal line driving circuit is formed.

When the source signal line driving circuit and the gate signal linedriving circuit are arranged as described above, the followingstructures are employed to sequentially scan the gate signal lines inthe pixel region.

In a first structure, the gate signal line driving circuit outputssignals to lead-out gate signal lines that are perpendicular to the gatesignal lines in the pixel region.

If the gate signal line driving circuit and the source signal linedriving circuit are on the same side of the pixel region while placingthe source signal line driving circuit nearer to the pixel region thanthe gate signal line driving circuit, the lead-out gate signal lines areled into the pixel region piercing through the source signal linedriving circuit that is interposed between the gate signal line drivingcircuit and the pixel region.

The lead-out gate signal lines are respectively connected to theirassociated gate signal lines in the pixel region. In this way, the gatesignal line driving circuit sequentially inputs signals to the gatesignal lines in the pixel region.

In the pixel region, the lead-out gate signal lines connected to thegate signal lines may be formed on the same layer where the gate signallines are formed or may be formed on a different layer.

The lead-out gate signal lines are in parallel with the source signallines in the pixel region. By forming the lead-out gate signal lines soas to overlap the parallel wiring lines, the aperture ratio can beincreased.

In a second structure, an output of the gate signal line driving circuitis led into the pixel region in a lateral direction.

In this case, a seal member can be placed above the gate signal lines.The area the wiring lines occupy is thus reduced and the area of theframe in the lateral direction of the display device is reducedaccordingly.

With the above-described structures, the area the gate signal linedriving circuit occupies in prior art is removed to reduce the width(side to side) of the display device. Therefore a display device thathas a small frame area in the lateral direction can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1C are diagrams showing a structure of a display deviceaccording to the present invention;

FIGS. 2A and 2B are diagrams showing a wiring structure of a pixel of adisplay device according to the present invention;

FIGS. 3A to 3J are diagrams showing the structure of a display deviceaccording to the present invention;

FIG. 4 is a schematic diagram showing the structure of a display deviceaccording to the present invention;

FIGS. 5A to 5C are diagrams showing the wiring structure of a pixel of adisplay device according to the present invention;

FIGS. 6A to 6D are diagrams showing the structure of a pixel of a liquidcrystal display device according to Embodiment 1;

FIGS. 7A to 7E are diagrams showing the structure of a pixel of an OLEDdisplay device according to Embodiment 2;

FIGS. 8A to 8E are diagrams showing the structure of a pixel of an OLEDdisplay device according to Embodiment 3;

FIG. 9 is a diagram showing a structure of a conventional displaydevice;

FIG. 10 is a circuit diagram showing the structure of a pixel of aliquid crystal display device according to Embodiment 1;

FIG. 11 is a circuit diagram showing the structure of a pixel of an OLEDdisplay device according to Embodiment 2;

FIG. 12 is a circuit diagram showing the structure of a pixel of an OLEDdisplay device according to Embodiment 3;

FIGS. 13A to 13F are diagrams showing the structure of a display deviceaccording to Embodiment 4;

FIGS. 14A and 14B are diagrams showing electronic equipment using adisplay device of the present invention in Embodiment 6;

FIGS. 15A to 15D are diagrams showing the structure of a seal member anda led-out part of gate signal lines in a display device of the presentinvention; and

FIGS. 16A and 16B are sectional views each showing the structure of apixel of an OLED display device according to the Embodiment 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment Mode 1

In a display device with driving circuits (a source signal line drivingcircuit and a gate signal line driving circuit) for controlling signalsto be inputted to a plurality of pixels being formed on the sameinsulating surface where the plural pixels are formed, the gate signalline driving circuit and the source signal line driving circuit areplaced on the same side out of four sides of a pixel region. The sourcesignal line driving circuit is placed nearer to the pixel region thanthe gate signal line driving circuit, and signals from the gate signalline driving circuit are inputted to the pixel region through the sourcesignal line driving circuit.

No driving circuits (source signal line driving circuit and gate signalline driving circuit) are placed to the left and right of the pixelregion.

FIGS. 1A to 1C show a structure of Embodiment Mode 1 of the presentinvention.

FIG. 1A is a top view showing the structure of a display device. Thedisplay device has a pixel substrate 100 on which a pixel region 103, asource signal line driving circuit 102, a gate signal line drivingcircuit 101, an FPC substrate 104, and a seal member 106 are arranged.

The source signal line driving circuit 102 is formed above the pixelregion 103. The gate signal line driving circuit 101 is formed above thepixel region 103 in parallel to the source signal line driving circuit102.

A detailed structure of a region denoted by 110 in FIG. 1A is shown inFIG. 1B and a detailed structure of a region denoted by 111 is shown inFIG. 1C.

Denoted by 101 a in FIG. 1B is a part of the gate signal line drivingcircuit 101. 102 a denotes a part of the source signal line drivingcircuit 102. In the pixel region here, x (x is a natural number) sourcesignal lines and y (y is a natural number) gate signal lines arearranged.

In the region 110, signals outputted from the gate signal line drivingcircuit 101 a are inputted to lead-out gate signal lines GDi−2 to GDi+2(i is a natural number equal to or larger than 3). The lead-out gatesignal lines GDi−2 to GDi+2 are led into the pixel region 103 whilepiercing through the source signal line driving circuit 102 a. Thesource signal line driving circuit 102 a outputs signals to sourcesignal lines Sj−2 to Sj+2 (j is a natural number equal to or larger than3). The source signal lines Sj−2 to Sj+2 are arranged in parallel to thelead-out gate signal lines GDi−2 to GDi+2.

The signal lines led from the source signal line driving circuit intothe pixel region may be called lead-out source signal lines anddiscriminated from the source signal lines arranged in the pixel region103. However, the lead-out source signal lines and the source signallines in the pixel region here are generically called as source signallines for the sake of explanation.

In the region 111 shown in FIG. 10, the lead-out gate signal lines GDi−2to GDi+2 led into the pixel region 103 are connected to the gate signallines Gi−2 to Gi+2, respectively.

The source signal lines and others are not shown in FIG. 1C.

Similar to the region 110, signals are inputted from the whole gatesignal line driving circuit 101 to all of the lead-out gate signal linesGD1 to GDz (z is a natural number) to input the signals to the pixelregion. Signals are inputted from the whole source signal line drivingcircuit 102 to the source signal lines S1 to Sx to input the signals tothe pixel region 103. Similar to the region 111, the gate signal linesG1 to Gy are associated with and connected to the lead-out gate signallines GD1 to GDz, respectively, in the pixel region 103.

Here, it is assumed that the number of lead-out gate signal lines, z, isidentical with the number of gate signal lines, y.

Generally, the number of source signal lines, x, is different from thenumber of gate signal lines, y. If the number x of the source signallines is larger than the number y of the gate signal lines, there are anarea where the source signal lines and lead-out gate signal lines arealternately led into the pixel region and an area where the sourcesignal lines alone are led into the pixel region. Otherwise, the wiringline interval of the lead-out gate signal lines is wider than the wiringline interval of the source signal lines.

The states described above can cause fluctuation in luminance betweenpixels when the aperture ratio of pixels matters in a transmissivedisplay device. Then the number of lead-out gate signal lines, z, may beset equal to the number of source signal lines, x, and (x−y) lead-outgate signal lines serve as dummy wiring lines to which no signals areinputted.

A first structure of Embodiment Mode 1 will be described in whichlead-out gate signal lines are formed on the same layer where gatesignal lines are formed.

FIGS. 2A and 2B are top views showing a structure of a part of a pixelregion.

In FIG. 2A, lead-out gate signal lines GDi−1 to GDi+1 and gate signallines Gi−1 to Gi+1 are formed on the same layer. The gate signal line Giis connected to the lead-out gate signal line GDi. On the other hand,the gate signal line Gi is not connected to a lead-out gate signal lineGDj (j is a natural number equal to or less than y but not equal to i)and the lines Gi and GDj intersect each other through a wiring lineformed on a layer different from the layer where the gate signal line Giis formed.

In this way, the lead-out gate signal lines GD1 to GDy are connected tothe gate signal lines G1 to Gy, respectively, throughout the pixelregion.

FIG. 2B is an enlarged view of a region denoted by 200 in FIG. 2A.

The lead-out gate signal line GDi intersects the gate signal line Gi−1through a wiring line 201 formed on a layer different from the layer onwhich the gate signal lines Gi and Gi−1 are formed. In other words,before intersecting the gate signal line Gi−1, the lead-out gate signalline GDi that is formed on the same layer where the gate signal lineGi−1 is formed is connected to the wiring line 201 by a contact hole 202a. After the lead-out gate signal line GDi intersects the gate signalline Gi−1, the wiring line 201 is again connected by a contact hole 202b to the lead-out wiring line GDi that is formed on the same layer wherethe gate signal line Gi−1 is formed. The lead-out gate signal line GDiand the gate signal line Gi are connected to each other in this way.

The structure shown in FIGS. 2A and 2B is effective for a display devicein which emitted light does not travel through a pixel substrate to beviewed, such as reflective liquid crystal display devices and upwardemission OLED display devices.

Described next is a second structure of Embodiment Mode 1 in whichlead-out gate signal lines and gate signal lines are formed on differentlayers. The description will be given with reference to FIGS. 5A to 5C.

FIGS. 5A to 5C are top views showing the structure of a part of a pixelregion.

As shown in FIG. 5A, the lead-out gate signal lines GDi and GDi+1 areformed on a layer different from the layer on which the gate signallines Gi and Gi+1 are formed. Wiring lines other than lead-out gatesignal lines and gate signal lines are not shown in FIG. 5A.

The lead-out gate signal line GDi and the gate signal line Gi areconnected to each other through a contact hole 501 i. Similarly, thelead-out gate signal line GDi+1 and the gate signal line Gi+1 areconnected to each other through a contact hole 501 i+1.

FIG. 5B shows an example in which source signal lines Si and Si+1 arearranged so as to overlap the lead-out gate signal lines GDi and GDi+1.In this case, the source signal lines Si and Si+1, the gate signal linesGi and Gi+1, and the lead-out gate signal lines GDi and GDi+1 are formedon three different layers. One pixel is denoted by 500.

The lead-out gate signal line GDi and the gate signal line Gi areconnected to each other through a contact hole 502 i. Similarly, thelead-out gate signal line GDi+1 and the gate signal line Gi+1 areconnected to each other through a contact hole 502 i+1.

In the structure of FIG. 5B where the power supply lines are arranged tooverlap the lead-out gate signal lines, the aperture ratio of pixels canbe raised. The structure shown in FIG. 5B is effective for a displaydevice in which light viewed is emitted through a pixel substrate, suchas transmissive liquid crystal display devices and downward emissionOLED display devices.

FIG. 5C shows an example in which power supply lines Vi and Vi+1 arearranged so as to overlap the lead-out gate signal lines GDi and GDi+1.In this case, the power supply lines Vi and Vi+1, the gate signal linesGi and Gi+1, and the lead-out gate signal lines GDi and GDi+1 are formedon three different layers. The power supply lines Vi and Vi+1 and thesource signal lines Si and Si+1 may be formed on the same layer ordifferent layers. One pixel is denoted by 500.

The lead-out gate signal line GDi and the gate signal line Gi areconnected to each other through a contact hole 503 i. Similarly, thelead-out gate signal line GDi+1 and the gate signal line Gi+1 areconnected to each other through a contact hole 503 i+1.

In the structure of FIG. 5C where the power supply lines are arranged tooverlap the lead-out gate signal lines, the aperture ratio of pixels canbe raised. The structure shown in FIG. 5C is effective for a displaydevice in which light viewed is emitted through a pixel substrate, suchas transmissive liquid crystal display devices and downward emissionOLED display devices.

In Embodiment Mode 1, the gate signal line driving circuit is placedabove the source signal line driving circuit so that the source signalline driving circuit comes nearer to the pixel region than the gatesignal line driving circuit. Alternatively, the gate signal line drivingcircuit may be placed nearer to the pixel region than the source signalline driving circuit.

In the display device shown in Embodiment Mode 1, the distance alongwhich the lead-out gate signal lines are led can be shortened.Accordingly, Embodiment Mode 1 is effective for a display device whosepixel region has a relatively large area.

This embodiment mode can be applied freely to display devices of anystructure as long as it has pixels driven by a driving circuit forselecting a pixel column (source signal line driving circuit) and adriving circuit for selecting a pixel row (gate signal line drivingcircuit). For example, this embodiment mode is applicable to liquidcrystal display devices and OLED display devices.

Pixels of a display device according to this embodiment mode can be ofany known structure as long as they are wired to signal lines forselecting a pixel column (source signal lines) and signal lines forselecting a pixel row (gate signal lines). Also, this embodiment modecan employ driving circuits of any known structure for the source signalline driving circuit and the gate signal line driving circuit.

For instance, the gate signal line driving circuit may be of the typethat is composed of a shift register and other components to outputsignals sequentially, or the type that is composed of a decoder andother components to output signals sequentially in an arbitrary order.

Embodiment Mode 2

According to Embodiment Mode 2, in a display device with drivingcircuits (a source signal line driving circuit and a gate signal linedriving circuit) for controlling signals to be inputted to a pluralityof pixels being formed on the same insulating surface where the pluralpixels are formed, the gate signal line driving circuit is arranged inparallel to the source signal line driving circuit and a signal outputfrom the gate signal line driving circuit is led through the peripheryof the source signal line driving circuit and the periphery of a pixelregion to be inputted to gate signal lines in the pixel region in alateral direction. A schematic diagram of the display device structuredas above is shown in FIG. 4.

In FIG. 4, the display device has a pixel substrate 300 on which gatesignal line driving circuits 301 (301A and 301B), a source signal linedriving circuit 302, a pixel region 303, an FPC substrate 304, and aseal member 306 are arranged.

The gate signal line driving circuits 301 (301A and 301B) are placedabove and below the pixel region 303 in parallel to the source signalline driving circuit 302. Output signals of the gate signal line drivingcircuits are inputted to gate signal lines in the pixel region 303 fromthe left and right of the pixel region 303 through wiring lines led in aregion denoted by 333 in FIG. 4.

Alternatively, only one gate signal line driving circuit 301 may beplaced above or below the pixel region 303.

If the seal member overlaps the gate signal lines that are led throughthe left and right of the pixel region 303, the lateral frame area ofthe display device can be reduced even more.

The signal lines led from the gate signal line driving circuits into thepixel region may be called lead-out gate signal lines and discriminatedfrom the gate signal lines arranged in the pixel region 303. However,the lead-out gate signal lines and the gate signal lines in the pixelregion here are generically called as gate signal lines for the sake ofexplanation.

FIGS. 15A to 15D are schematic diagrams showing an example in which gatesignal lines led out and a seal member are arranged to overlap eachother.

FIG. 15A is a top view of gate signal lines led through the left of apixel region. Gate signal lines G1 to Gy′ are arranged in parallel toone another and led through areas to the left of a pixel region 1510into the pixel region 1510. A seal member 1511 is formed above the gatesignal lines G1 to Gy′. FIG. 15B is a sectional view taken along theline A-A' in FIG. 15A. In FIG. 15B, the gate signal lines G1 to Gy′ areformed on an insulating surface 1501 on a pixel substrate 1500. The sealmember 1511 is formed on the gate signal lines G1 to Gy′.

The gate signal lines G1 to Gy′ that are arranged in parallel to oneanother by the side of the pixel region 1510 may all overlap the sealmember 1511 as shown in FIGS. 15A and 15B. Alternatively, only some ofthe gate signal lines G1 to Gy′ that are arranged in parallel to oneanother by the side of the pixel region 1510 may overlap the seal member1511. FIG. 15C shows a top view of a structure in which only some of thegate signal lines G1 to Gy′ which are arranged in parallel to oneanother and which are led by the side of the pixel region 1510 overlapthe seal member 1511. A sectional view taken along the line B-B' in FIG.15C is shown in FIG. 15D. In FIGS. 15C and 15D, components that areidentical with those in FIGS. 15A and 15B are denoted by the samereference symbols and explanations thereof are omitted.

FIGS. 15A to 15D show a structure in which a seal member is in contactwith gate signal lines. However, the seal member and the gate signallines may overlap each other while sandwiching an interlayer film or thelike therebetween.

If the display device shown in FIGS. 15A to 15D is a liquid crystaldisplay device, an opposite substrate, an orientated film, a liquidcrystal material, and the like are omitted from the drawings. If thedisplay device shown in FIGS. 15A to 15D is an OLED display device, acover member and the like are omitted from the drawings.

The above-mentioned structure in which the led-out portions of the gatesignal lines are arranged to overlap the seal member makes it possibleto reduce the frame area even when the display device has a large numberof gate signal lines.

FIGS. 3A to 3J show an example of specific structure of a display deviceaccording to Embodiment Mode 2.

In FIG. 3A, components that are identical with those in FIG. 4 aredenoted by the same reference symbols and explanations thereof areomitted.

The gate signal line driving circuit 301A is placed above the sourcesignal line driving circuit 302, which is placed above the pixel region303. The gate signal line driving circuit 301B is placed below the pixelregion 303.

Output signals of the gate signal line driving circuits 301A and 301Bare led through the periphery of the source signal line driving circuit302 and the periphery of the pixel region 303 to be inputted to thepixel region 303.

A detailed description will be given with reference to FIGS. 3B to 3J ona specific example of leading gate signal lines for inputting outputsignals of the gate signal line driving circuits 301A and 301B to thepixel region.

The number of gate signal lines placed in the pixel region isrepresented by y (y is a natural number). Here, y is a multiple of 4 forthe sake of explanation, but the present invention is not limitedthereto.

The gate signal line driving circuit 301A is divided into two blocks,301A_1 and 301A_2. The gate signal line driving circuit 301B is dividedinto two blocks, 301B_1 and 301B_2. The gate signal line driving circuit301A_1 is a circuit for inputting signals to the first to y/4-th gatesignal lines G1 to G(y/4) placed in the pixel region 303. An area of thepixel region where the gate signal lines G1 to G(y/4) are placed isdenoted by 303_1. The gate signal line driving circuit 301A_2 is acircuit for inputting signals to the (y/4+1)-th to (y/2)-th gate signallines G(y/4+1) to G(y/2) placed in the pixel region 303. An area of thepixel region where the gate signal lines G(y/4+1) to G(y/2) are placedis denoted by 303_2. The gate signal line driving circuit 301B_1 is acircuit for inputting signals to the (y/2+1)-th to (3y/4)-th gate signallines G(y/2+1) to G(3y/4) placed in the pixel region 303. An area of thepixel region where the gate signal lines G(y/2+1) to G(3y/4) are placedis denoted by 303_3. The gate signal line driving circuit 301B_2 is acircuit for inputting signals to the (3y/4+1)-th to y-th gate signallines G (3y/4+1) to Gy placed in the pixel region 303. An area of thepixel region where the gate signal lines G(3y/4+1) to Gy are placed isdenoted by 303_4.

First, a detailed description is given about wiring lines for inputtingoutput signals of the gate signal line driving circuit 301A_1 to theregion 303_1. FIGS. 3B to 3D respectively show detailed structures ofregions denoted by 311 a, 312 a, and 313 a in FIG. 3A.

As shown in FIG. 3B, signals outputted from a part of the gate signalline driving circuit 301A_1, namely, 301Aa, are inputted to the gatesignal lines Gi−2 to Gi+2. The gate signal lines Gi−2 to Gi+2 can changetheir direction between the gate signal line driving circuit 301Aa and apart of the source signal line driving circuit 302, namely, 302 a. Inthis way, signals outputted from the gate signal line driving circuit301A_1 are led to the left end of the source signal line driving circuit302 through the gate signal lines G1 to G(y/4) that are formed inparallel with one another between the source signal line driving circuit302 and the gate signal line driving circuit 301A_1. Once the gatesignal lines G1 to G(y/4) are led to the left end of the source signalline driving circuit 302, their direction is changed and signals are ledthrough the left region of the pixel region 303 that overlaps the sealmember 306 to the left side of the region 303_1 to be inputted to theregion 303_1. FIG. 3C shows a part of the seal member 306, 306 a, and apart of the region 303_1, 303 a. As shown in FIG. 3D, signals are thusinputted to the gate signal lines Gi−2 to Gi+2 that are perpendicular tothe source signal lines (represented by S in the drawing) in the pixelregion 303_1.

Next, a detailed description is given about wiring lines for inputtingoutput signals of the gate signal line driving circuit 301A_2 to theregion 303_2. FIGS. 3E to 3G respectively show detailed structures ofregions denoted by 311 b, 312 b, and 313 b in FIG. 3A.

As shown in FIG. 3E, signals outputted from a part of the gate signalline driving circuit 301A_2, namely, 301Ab, are inputted to the gatesignal lines Gj−2 to Gj+2. The gate signal lines Gj−2 to Gj+2 can changetheir direction between the gate signal line driving circuit 301Ab and apart of the source signal line driving circuit 302, namely, 302 b. Inthis way, signals outputted from the gate signal line driving circuit301A_2 are led to the right end of the source signal line drivingcircuit 302 through the gate signal lines G(y/4)+1 to G(y/2) that areformed in parallel with one another between the source signal linedriving circuit 302 and the gate signal line driving circuit 301A_2.Once the gate signal lines G1 to G(y/4) are led to the right end of thesource signal line driving circuit 302, their direction is changed andsignals are led through the right region of the pixel region 303 thatoverlaps the seal member 306 to the right side of the region 303_2 to beinputted to the region 303_2. FIG. 1F shows a part of the seal member306, 306 b, and a part of the region 303_1, 303 b. As shown in FIG. 3G,signals are thus inputted to the gate signal lines Gj−2 to Gj+2 that areperpendicular to the source signal lines (represented by S in thedrawing) in the pixel region 303_2.

A detailed description is given about wiring lines for inputting outputsignals of the gate signal line driving circuit 301B_1 to the region303_3. FIGS. 3H to 3J respectively show detailed structures of regionsdenoted by 311 c, 312 c, and 313 c in FIG. 3A.

As shown in FIG. 3H, signals outputted from a part of the gate signalline driving circuit 301B_1, namely, 301Ba, are inputted to gate signallines Gk−2 to Gk+2. The gate signal lines Gk−2 to Gk+2 can change theirdirection between the gate signal line driving circuit 301Ba and a partof the pixel region 303_4, namely, 303 c. In this way, signals outputtedfrom the gate signal line driving circuit 301B_1 are led to the left endof the pixel region 303 through the gate signal lines G(y/2+1) toG(3y/4) that are formed in parallel with one another between the pixelregion 303 and the gate signal line driving circuit 301B_1. Once thegate signal lines G(y/2+1) to G(3y/4) are led to the left end of thepixel region 303, their direction is changed and signals are led throughthe left region of the pixel region 303 that overlaps the seal member306 to the left side of the region 303_3 to be inputted to the region303_3. FIG. 3I shows a part of the seal member 306, 306 c, and a part ofthe region 303_3, 303 c. As shown in FIG. 3J, signals are thus inputtedto the gate signal lines Gi−2 to Gi+2 that are perpendicular to thesource signal lines (represented by S in the drawing) in the pixelregion 303_3.

Similarly, though not shown in the drawings, signals outputted from thegate signal line driving circuit 301B_2 are led between the gate signalline driving circuit 301B_2 and the pixel region 303_4 to the right endof the pixel region 303. Then the direction is changed and the signalsare led through the right region of the pixel region 303 that overlapsthe seal member 306 to the right end of the region 303_4 to be inputtedto the region 303_4.

At this point, the gate signal line driving circuits 301A_1, 301A_2,301B_1, and 301B_2 separately scan to output signals to the gate signallines G1 to Gy sequentially. In this way signals are sequentiallyinputted to the gate signal lines G1 to Gy in the pixel region 303.

Since the above-described structure has no gate signal line drivingcircuit by the side of the pixel region, the frame area can be reducedfurther in the lateral direction of the pixel region. If the seal memberis formed above the gate signal lines that are led through the left andright of the pixel region, the width of the left and right borders ofthe frame of the display device can be reduced even more.

When gate signal lines are led in four directions, namely, upper left,upper right, lower left, and lower right of a pixel region as in theabove-described structure, y/4 gate signal lines at the most arearranged in parallel with one another to the left and right of the pixelregion, respectively. If a gate signal line driving circuit is placedonly above a pixel region and gate signal lines are led in one directionfrom upper left of the pixel region, y gate signal lines at the most arearranged in parallel with one another to the left of the pixel region.

By leading gate signal lines to a pixel region from several directionsas in this embodiment mode, the number of wiring lines arranged inparallel to one another by the side of the pixel region can be reduced.This makes it possible to further reduce the frame area in the lateraldirection of the pixel region.

Signal lines for inputting signals to the driving circuits (sourcesignal line driving circuit 302 and gate signal line driving circuits301) from the FPC substrate and power supply lines are formed on a layerdifferent from the layer on which the gate signal lines led through theperiphery of the pixel region 303 are formed.

Unlike Embodiment Mode 1, signals outputted from the gate signal linedriving circuits have to be led to the left and right of the pixelregion 303 in Embodiment Mode 2. Accordingly, the distance along whichthe gate signal lines G1 to Gy are led is long particularly in a displaydevice that has a large pixel region. However, this embodiment mode doesnot need to place in the pixel region lead-out gate signal linesperpendicular to gate signal lines, and therefore can increase theaperture ratio in a transmissive display device. In addition, thisembodiment mode does not require the lead-out gate signal lines topierce through the source signal line driving circuit, and therefore hasless limitation on the arrangement of the source signal line drivingcircuit.

Consequently, Embodiment Mode 2 is effective for a display device thathas a rather small pixel region.

This embodiment mode can be applied freely to display devices of anystructure as long as it has pixels driven by a driving circuit forselecting a pixel column (source signal line driving circuit) and adriving circuit for selecting a pixel row (gate signal line drivingcircuit). For example, this embodiment mode is applicable to liquidcrystal display devices and OLED display devices.

Pixels of a display device according to this embodiment mode can be ofany known structure as long as they are wired to signal lines forselecting a pixel column (source signal lines) and signal lines forselecting a pixel row (gate signal lines). Also, this embodiment modecan employ driving circuits of any known structure for the source signalline driving circuit and the gate signal line driving circuit.

For instance, the gate signal line driving circuit may be of the typethat is composed of a shift register and other components to outputsignals sequentially, or the type that is composed of a decoder andother components to output signals sequentially in an arbitrary order.

Embodiment 1

Embodiment 1 shows an example of a liquid crystal display devicestructured as shown in FIG. 5B as the second structure of EmbodimentMode 1.

FIG. 10 is a circuit diagram showing the structure of a pixel accordingto this embodiment.

In FIG. 10, a source signal line 602_1, a gate signal line 603_1, aswitching TFT 607, and a capacitor element (capacitor storage) 608 arearranged in one pixel 600.

Denoted by 603_1 to 603_3 are gate signal lines. 601_1 to 601_3 arelead-out gate signal lines. 606_1 to 606_3 are common lines.

In this embodiment, the switching TFT 607 is a dual-gate TFT that has afirst gate electrode and a second gate electrode. One of the first andsecond gate electrodes of the switching TFT 607 receives an electricpotential V_(com) and the other is connected to the gate signal line603_1.

The switching TFT 607 has a source region and a drain region one ofwhich is connected to the source signal line 602_1 and the other ofwhich is connected to one of electrodes of the capacitor storage 608 andto a liquid crystal element 609. The other electrode of the capacitorstorage 608 is connected to the common line 606_1.

The gate signal line 603_1 is connected to the lead-out gate signal line601_1 through a contact hole 605_1. Similarly, the gate signal line603_2 is connected to the lead-out gate signal line 601_2 through acontact hole 605_2. The gate signal line 603_3 is connected to thelead-out gate signal line 601_3 through a contact hole 605_3.

FIGS. 6A to 6D are a top view and a sectional view of the pixel in theliquid crystal display device which is structured as shown in FIG. 10.

In FIGS. 6A to 6D, components that are identical with those in FIG. 10are denoted by the same reference symbols and explanations thereof areomitted. Of the liquid crystal element, only the pixel electrode denotedby 609 is shown in FIGS. 6A to 6D and its opposing substrate, liquidcrystal layer, alignment layer and the like are omitted.

FIG. 6A is a top view of the liquid crystal display device. FIG. 6B is asectional view taken along the line A-A' in FIG. 6A. FIG. 6C is asectional view taken along the line B-B' in FIG. 6A. FIG. 6D is asectional view taken along the line C-C' in FIG. 6A.

As shown in FIG. 6B, 668 a that is one of the source region and drainregion of the switching TFT 607 formed on a pixel substrate 666 isconnected to a source signal line 602_1 whereas the other, 668 c, isconnected to one of the electrode of the capacitor storage 608 and thepixel electrode 609 through a wiring line 612. Here, the capacitorstorage 608 is structured by an electrode 613 formed by thesemiconductor layer and the common line 606_1 with an insulting film 669sandwiched therebetween. Denoted by 670 is an interlayer film.

The switching TFT 607 is a dual-gate TFT having a first gate electrode603_1 a adjacent to a channel portion 668 b with an insulating film 669sandwiched there between and a second gate electrode 610 a adjacent to achannel portion 668 b with an insulating film 667 sandwichedtherebetween. The first gate electrode 603_1 a is a part of the gatesignal line 603_1. The second gate electrode 610 a is a part of a wiringline 610 that receives an electric potential V.

The lead-out gate signal line 601_1 is formed to overlap the powersupply line 602_1.

As shown in FIG. 6C, a wiring line 610 for giving an electric potentialV_(com) to the second gate electrode 610 a of the switching TFT 607 isconnected to a wiring line 614 through a contact hole 611. The wiringline 610 is led above the lead-out gate signal line 601_2.

As shown in FIG. 6D, the lead-out gate signal line 601_2 is connected tothe gate signal line 603_2 through a contact hole 605_2.

When the TFTs placed in each pixel are dual-gate TFTs as in theabove-described structure, of the gate electrodes of each TFT which areformed on different layers, gate signal lines can be formed on a layerwhere one of the gate electrodes is formed whereas lead-out gate signallines are formed on a layer where the other gate electrode is formed.

Embodiment 2

Embodiment 2 shows an example of the OLED display device structured asshown in FIG. 5C as the second structure of Embodiment Mode 1.

FIG. 11 is a circuit diagram showing the structure of a pixel accordingto this embodiment.

In FIG. 11, a source signal line 704_1, a gate signal line 703_1, apower supply line 702_2, a switching TFT 706, a driving TFT 707, and acapacitor element (capacitor storage) 708 are arranged in one pixel 700.

Denoted by 703_1 to 703_3 are gate signal lines 701_1 to 701_3 arelead-out gate signal lines 704_1 to 704_3 are source signal lines 702_1to 702_3 are power supply lines.

In this embodiment, the switching TFT 706 is a dual-gate TFT that has afirst gate electrode and a second gate electrode. One of the first andsecond gate electrodes of the switching TFT 706 receives an electricpotential V_(com) and the other is connected to the gate signal line703_1.

The driving TFT 707 is also a dual-gate TFT that has a first gateelectrode and a second gate electrode. The first gate electrode of thedriving TFT 707 and the second gate electrode thereof are connected toeach other.

The dispersion of characteristic of TFT can be reduced by using dualgate TFT. For driving TFT 707, there is an especially necessity toreduce the dispersion of characteristic of TFT. Therefore, using thedual gate TFT 707 is an effective means.

The switching TFT 706 has a source region and a drain region one ofwhich is connected to the source signal line 704_1 and the other ofwhich is connected to one of electrodes of the capacitor storage 708 andto the gate electrodes (first gate electrode and second gate electrode)of the driving TFT 707. The other electrode of the capacitor storage 708is connected to the power supply line 702_2. The driving TFT 707 has asource region and a drain region one of which is connected to the powersupply line 702_2 and the other of which is connected to one ofelectrodes (pixel electrode) of an CLOD element 709.

The gate signal line 703_1 is connected to the lead-out gate signal line701_1 through a contact hole 705_1. Similarly, the gate signal line703_2 is connected to the lead-out gate signal line 701_2 through acontact hole 705_2. The gate signal line 703_3 is connected to thelead-out gate signal line 701_3 through a contact hole 705_3.

FIGS. 7A to 7E are a top view and a sectional view of the pixel in theOLED display device which is structured as shown in FIG. 11.

In FIGS. 7A to 7E, components that are identical with those in FIG. 11are denoted by the same reference symbols and explanations thereof areomitted. Of the OLED element, only the pixel electrode denoted by 709 isshown in FIGS. 7A to 7E and its OLED layer, cover member, and the likeare omitted.

FIG. 7A is a top view of the OLED display device. FIG. 7B is a sectionalview taken along the line A-A' in FIG. 7A. FIG. 7C is a sectional viewtaken along the line B-B' in FIG. 7A. FIG. 7D is a sectional view takenalong the line C-C' in FIG. 7A. FIG. 7E is a sectional view taken alongthe line D-D' in FIG. 7A.

As shown in FIG. 7B, 779 a that is one of the source region and drainregion of the switching TFT 706 formed on a pixel substrate 777 isconnected to a source signal line 704_1 whereas the other, 779 c, isconnected to wiring lines 715 and 716 through a wiring line 712. Denotedby 781 is an interlayer film.

The switching TFT 706 is a dual-gate TFT having a first gate electrode703_1 a adjacent to a channel portion 779 b with an insulating film 780sandwiched there between and a second gate electrode 710 a adjacent to achannel portion 779 b with an insulating film 778 sandwiched therebetween. The first gate electrode 703_1 a is a part of the gate signalline 703_1. The second gate electrode 710 a is apart of a wiring line710 that receives an electric potential V_(com).

The lead-out gate signal line 701_1 is formed to overlap the powersupply line 702_1.

As shown in FIG. 7C, 782 a that is one of the source region and drainregion of the driving TFT 707 is connected to a pixel electrode 709through a wiring line 717 whereas the other, 782 c, is connected to apower supply line 702_2. In addition, the lead out gate signal line701_2 is formed to overlap the power supply line 702_2.

The driving TFT 707 is a dual-gate TFT having a first gate electrode 715a adjacent to a channel portion 782 b with an insulating film 780sandwiched there between and a second gate electrode 716 a adjacent to achannel portion 782 b with an insulating film 778 sandwiched therebetween. The first gate electrode 715 a is a part of the wiring line715. The second gate electrode 716 a is a part of a wiring line 716.Further, the wiring line 715 and the wiring line 716 are connected toeach other (refer to FIG. 7D).

As shown in FIG. 7D, the wiring lines 715 and 716 are connected eachother. The wiring line 715 serves as one of the electrodes of thecapacitor storage 708. The other electrode of the capacitor storage is783 that is formed of a semiconductor layer 783 is connected to thepower supply line 702_2 through a contact hole 784.

The lead-out gate signal line 701_2 is connected to the gate signal line703_2 through a contact hole 705_2.

As shown in FIG. 7E, a wiring line 710 for giving an electric potentialV_(com) to the second gate electrode 710 a of the switching TFT 706 isconnected to a wiring line 714 through a contact hole 711. The wiringline 710 is led above the lead-out gate signal line 701_2.

When the TFTs placed in each pixel are dual-gate TFTs as in theabove-described structure, of the gate electrodes of each TFT which areformed on different layers, gate signal lines can be formed on a layerwhere one of the gate electrodes is formed whereas lead-out gate signallines are formed on a layer where the other gate electrode is formed.

Embodiment 3

An example of the second structure has been given in Embodiment 2. Thisembodiment shows another example of the OLED display device structuredas shown in FIG. 5C as the second structure of Embodiment Mode 1.

FIG. 12 is a circuit diagram showing the structure of a pixel accordingto this embodiment. In FIG. 12, components that are identical with thosein FIG. 11 are denoted by the same reference symbols.

In FIG. 12, a source signal line 704_1, a gate signal line 703_1, apower supply line 702_2, a switching TFT 706, a driving TFT 707, anerasing TEE 722, and a capacitor element (capacitor storage) 708 arearranged in one pixel 724.

Denoted by 703_1 to 703_3 are gate signal lines 701_1 to 701_3 arelead-out gate signal lines 721_1 to 721_3 are erasing gate signal lines720_1 to 720_3 are lead-out erasing gate signal lines 704_1 to 704_3 aresource signal lines 702_1 to 702_3 are power supply lines.

In this embodiment, the switching TFT 706 is a dual-gate TFT that has afirst gate electrode and a second gate electrode. One of the first andsecond gate electrodes of the switching TFT 706 receives an electricpotential V_(com) and the other is connected to the gate signal line703_1.

The driving TFT 707 is also a dual-gate TFT that has a first gateelectrode and a second gate electrode. The first gate electrode of thedriving TFT 707 and the second gate electrode thereof are connected toeach other.

Erasing TFT 722 too is a dual-gate TFT that has a first gate electrodeand a second gate electrode. One of the first and second gate electrodesof the erasing TFT 722 receives an electric potential V_(com) and theother is connected to the erasing gate signal line 721_1.

The switching TFT 706 has a source region and a drain region one ofwhich is connected to the source signal line 704_1 and the other ofwhich is connected to one of electrodes of the capacitor storage 708 andto the gate electrodes (first gate electrode and second gate electrode)of the driving TFT 707. The other electrode of the capacitor storage 708is connected to the power supply line 702_2. The driving TFT 707 has asource region and a drain region one of which is connected to the powersupply line 702_2 and the other of which is connected to one ofelectrodes (pixel electrode) of an OLED element 709.

The erasing TFT 722 has a source region and a drain region one of whichis connected to the power supply line 702_2 and the other of which isconnected to the gate electrodes (first gate electrode and second gateelectrode) of the driving TFT 707.

The gate signal line 703_1 is connected to the lead-out gate signal line701_1 through a contact hole 705_1. Similarly, the gate signal line703_2 is connected to the lead-out gate signal line 701_2 through acontact hole 705_2. The gate signal line 703_3 is connected to thelead-out gate signal line 701_3 through a contact hole 705_3.

The erasing gate signal line 721_1 is connected to the lead-out erasinggate signal line 720_1 through a contact hole 723_1. Similarly, theerasing gate signal line 721_2 is connected to the lead-out erasing gatesignal line 720_2 through a contact hole 723_2. The erasing gate signalline 721_3 is connected to the lead-out erasing gate signal line 720_3through a contact hole 723_3.

FIGS. 8A to 8E are a top view and sectional views of the pixel in theOLED display device which is structured as shown in FIG. 12.

In FIGS. 8A to 8E, components that are identical with those in FIG. 12are denoted by the same reference symbols and explanations thereof areomitted. Of the OLED element, only the pixel electrode denoted by 709 isshown in FIGS. 8A to 8E and its OLED layer, cover member, and the likeare omitted.

FIG. 8A is a top view of the OLED display device. FIG. 8B is a sectionalview taken along the line A-A' in FIG. 8A. FIG. 8C is a sectional viewtaken along the line C-C' in FIG. 8A. FIG. 8D is a sectional view takenalong the line E-E' in FIG. 8A. FIG. 8E is a sectional view taken alongthe line D-D' in FIG. 8A. A sectional view taken along the line B-B' inFIG. 8A is identical with FIG. 7C.

As shown in FIG. 8B, 779 a that is one of the source region and drainregion of the switching TFT 706 formed on a pixel substrate 777 isconnected to a source signal line 704_1 whereas the other, 779 c, isconnected to wiring lines 715 and 716 through a wiring line 712. Denotedby 781 is an interlayer film.

The switching TFT 706 is a dual-gate TFT having a first gate electrode703_1 a adjacent to a channel portion 779 b with an insulating film 780sandwiched therebetween and a second gate electrode 710 a adjacent to achannel portion 779 b with an insulating film 778 sandwichedtherebetween. The first gate electrode 703_1 a is a part of the gatesignal line 703_1. The second gate electrode 710 a is a part of a wiringline 710 that receives an electric potential V_(com).

The lead-out gate signal line 701_1 is formed to overlap the powersupply line 702_1. Also, the lead-out erasing gate signal line 720_1 isformed to overlap the source signal line 704_1.

As shown in FIG. 7C, the wiring lines 715 and 716 are connected. Thewiring line 715 serves as one of the electrodes of the capacitor storage708. The other electrode of the capacitor storage is 783 that is formedof a semiconductor layer. 783 is connected to the power supply line702_2 through a contact hole 784.

The lead-out gate signal line 701_2 is connected to the gate signal line703_2 through a contact hole 705_2.

As shown in FIG. 8D, 799 a that is one of the source region and drainregion of the erasing TFT 722 is connected to the wiring line 715whereas the other, 799 c, is connected to the power supply line 702_2.

The erasing TFT 722 is a dual-gate TFT having a first gate electrode721_1 a adjacent to a channel portion 799 b with an insulating film 780sandwiched therebetween and a second gate electrode 710 a adjacent to achannel portion 799 b with an insulating film 778 sandwichedtherebetween. The first gate electrode 721_1 a is a part of the erasinggate signal line 721_1. The second gate electrode 710 a is a part of awiring line 710 that receives an electric potential V_(com).

The lead-out erasing gate signal line 720_1 is formed to overlap asource signal line 704_1. The lead-out gate signal line 720_1 isconnected to the erasing gate signal line 721_1 through a contact hole723_1.

As shown in FIG. 7E, the wiring line 710 for giving an electricpotential V_(com) to the second gate electrode of the switching TFT 706and to the second gate electrode 710 a of the erasing TFT 722 isconnected to a wiring line 714 through a contact hole 711. The wiringline 710 is led above the lead-out gate signal line 701_2 and thelead-out erasing gate signal line 720_1.

When the TFTs placed in each pixel are dual-gate TFTs as in theabove-described structure, of the gate electrodes of each TFT which areformed on different layers, gate signal lines and erasing gate signallines can be formed on a layer where one of the gate electrodes isformed whereas lead-out gate signal lines and lead-out erasing gatesignal lines are formed on a Layer where the other gate electrode isformed.

Embodiment 4

An example of the display device of Embodiment Mode 2 has been shown inFIGS. 3A to 3J. This embodiment gives another specific example of thedisplay device structured as shown in FIG. 4 in Embodiment Mode 2.

FIGS. 13A to 13F show the structure of a display device according tothis embodiment. Components in FIGS. 13A to 13F that are identical withthose of Embodiment Mode 2 shown in FIGS. 3A to 3J are denoted by thesame reference symbols.

FIG. 13A is a top view of the display device. Gate signal line drivingcircuits 1301 (1301A and 1301B), a source signal line driving circuit302, a pixel region 303, an FPC substrate 304, and a seal member 306 arearranged on a pixel substrate 300.

Output signals of the gate signal line driving circuits 1301A and 1301Bare led through the periphery of the source signal line driving circuit302 and the periphery of the pixel region 303 and inputted to the pixelregion 303.

A specific example of leading gate signal lines for inputting to thepixel region 303 output signals of the gate signal line driving circuits1301A and 1301B will be described in detail with reference to FIGS. 13Bto 13F.

The number of gate signal lines placed in the pixel region isrepresented by y (y is a natural number). Here, y is a multiple of 4 forthe sake of explanation, but the present invention is not limitedthereto.

The gate signal line driving circuit 1301A is divided into two blocks,1301A_1 and 1301A_2. The gate signal line driving circuit 1301B isdivided into two blocks, 1301B_1 and 1301B_2.

The gate signal line driving circuit 1301A_1 is a circuit for inputtingsignals to even-numbered gate signal lines out of the first to (y/2)-thgate signal lines G1 to G(y/2) placed in the pixel region 303. The gatesignal line driving circuit 1301A_2 is a circuit for inputting signalsto odd-numbered gate signal lines out of the first to (y/2)-th gatesignal lines G1 to G(y/2) placed in the pixel region 303. An area of thepixel region 303 where the gate signal lines G1 to G(y/2) for receivingsignals outputted from the gate signal line driving circuits 1301A_1 and1301A_2 are placed is denoted by 303_A.

Similarly, the gate signal line driving circuit 1301B_1 is a circuit forinputting signals to even-numbered gate signal lines out of the(y/2+1)-th to y-th gate signal lines G(y/2+1) to Gy placed in the pixelregion 303. The gate signal line driving circuit 1301B_2 is a circuitfor inputting signals to odd-numbered gate signal lines out of the(y/2+1)-th to y-th gate signal lines G(y/2+1) to Gy placed in the pixelregion 303. An area of the pixel region 303 where the gate signal linesG(y/2+1) to Gy for receiving signals outputted from the gate signal linedriving circuits 1301B_1 and 1301B_2 are placed is denoted by 303_B.

First, a detailed description is given about wiring lines for inputtingoutput signals of the gate signal line driving circuit 1301A_1 to theregion 303_A. FIGS. 13B and 13C respectively show detailed structures ofregions denoted by 1311 a and 1312 a in FIG. 13A.

As shown in FIG. 13B, signals outputted from a part of the gate signalline driving circuit 1301A_1, namely, 1301Aa, are inputted to the gatesignal lines Gi−4, Gi−2, Gi, Gi+2, and Gi+4. The gate signal lines Gi−4,Gi−2, Gi, Gi+2, and Gi+4 can change their direction between the gatesignal line driving circuit 1301Aa and a part of the source signal linedriving circuit 302, namely, 302 a. In this way, signals outputted fromthe gate signal line driving circuit 1301A_1 are led to the left end ofthe source signal line driving circuit 302 through, odd-numbered gatesignal lines out of the gate signal lines G1 to G(y/2) that are formedin parallel to one another between the source signal line drivingcircuit 302 and the gate signal line driving circuit 1301A_1. Once thegate signal lines are led to the left end of the source signal linedriving circuit 302, their direction is changed and the signals are ledthrough the left region of the pixel region 303 that overlaps the sealmember 306 to the left side of the region 303_A to be inputted to theregion 303_A. FIG. 13C shows a part of the seal member 306, 306 a, and apart of the region 303_A, 303 a.

Next, a detailed description is given about wiring lines for inputtingoutput signals of the gate signal line driving circuit 1301A_2 to theregion 303_A. FIGS. 13D and 13E respectively show detailed structures ofregions denoted by 1311 b and 1312 b in FIG. 13A.

As shown in FIG. 13D, signals outputted from a part of the gate signalline driving circuit 1301A_2, namely, 1301Ab, are inputted to the gatesignal lines Gi−5, Gi−3, Gi−1, Gi+1, and Gi+3. The gate signal linesGi−5, Gi−3, Gi−1, Gi+1, and Gi+3 can change their direction between thegate signal line driving circuit 1301Ab and a part of the source signalline driving circuit 302, namely, 302 b.

In this way, signals outputted from the gate signal line driving circuit1301A_2 are led to the right end of the source signal line drivingcircuit 302 through odd-numbered gate signal lines out of the gatesignal lines G1 to G(y/2) that are formed in parallel to one anotherbetween the source signal line driving circuit 302 and the gate signalline driving circuit 1301A_2. Once the gate signal lines are led to theright end of the source signal line driving circuit 302, their directionis changed and the signals are led through the right region of the pixelregion 303 that overlaps the seal member 306 to the right side of theregion 303_A to be inputted to the region 303_A. FIG. 13E shows a partof the seal member 306, 306 b, and a part of the region 303_A, 303 b.

As shown in FIG. 13F, the above-described structure inputs signals tothe gate signal lines Gi−5 to G+4 that are perpendicular to the sourcesignal lines (represented by S in the drawing) in a part of the pixelregion 303_A, namely, 1313 ab.

Similarly, gate signal lines are led also from the gate signal linedriving circuits 1301B_1 and 1301B_2 to be connected to the gate signallines of the pixel region 303B.

In this way, signals from the gate signal line driving circuit 1301A and1301B are inputted to the gate signal lines G1 to Gy of the pixel region303.

Signal lines for inputting signals to the driving circuits (sourcesignal line driving circuit 302 and gate signal line driving circuits1301) from the FPC substrate and power supply lines are formed on alayer different from the layer on which the gate signal lines ledthrough the periphery of the pixel region 303 are formed.

This embodiment can be applied freely to display devices of anystructure as long as it has pixels driven by a driving circuit forselecting a pixel column (source signal line driving circuit) and adriving circuit for selecting a pixel row (gate signal line drivingcircuit). For example, this embodiment is applicable to liquid crystaldisplay devices and OLED display devices.

Pixels of a display device according to this embodiment can be of anyknown structure as long as they are wired to signal lines for selectinga pixel column (source signal lines) and signal lines for selecting apixel row (gate signal lines). Also, this embodiment can employ drivingcircuits of any known structure for the source signal line drivingcircuit and the gate signal line driving circuit.

For instance, the gate signal line driving circuit may be of the typethat is composed of a shift register and other components to outputsignals sequentially, or the type that is composed of a decoder andother components to output signals sequentially in an arbitrary order.

Embodiment 5

This embodiment shows an example of applying a display device of thepresent invention to an OLED display device.

FIGS. 16A and 16B are sectional views each showing the structure of anOLED display device according to the present invention. In thisembodiment, an OLED element and a driving TFT for flowing a draincurrent to the OLED element alone are shown as components thatconstitute a pixel of the OLED display device.

In this specification, an OLED element refers to an element with ananode and a cathode sandwiching an OLED layer that emits light by anelectro luminescence effect upon generation of electric field.

The term OLED element in this specification includes both an OLEDelement that utilizes light emission accompanying transition fromsinglet excitation to the base state (fluorescent light) and an OLEDelement that utilizes light emission accompanying transition fromtriplet excitation to the base state (phosphorescent light).

An OLED layer is made up of a hole injection layer, a hole transportinglayer, a light emitting layer, an electron transporting layer, anelectron injection layer, and the like. The basic structure of the OLEDelement is a laminate of an anode, a light emitting layer, and a cathodelayered in this order. The basic structure may be modified into astructure consisting of an anode, a hole injection layer, a lightemitting layer, an electron injection layer, and a cathode which arelayered in this order, or a structure consisting of an anode, a holeinjection layer, a hole transporting layer, a light emitting layer, anelectron transporting layer, an electron injection layer, and a cathodewhich are layered in this order.

In FIG. 16A, a driving TFT 1601 is formed on a pixel substrate 1600. Thedriving TFT 1601 is a dual-gate TFT that has a first gate electrode 1603a, a second gate electrode 1603 b, and a channel formation region 1604b. The channel formation region 1604 b is sandwiched between insulatingfilms 1602 and 1605, which are in turn sandwiched between the first andsecond gate electrodes. The driving TFT 1601 has a source region and adrain region, one of which is denoted by 1604 a and the other of whichis denoted by 1604 c. After the driving TFT 1601 is formed, aninterlayer film 1606 is formed.

The structure of the driving TFT 1601 is not limited to the one shown inthe drawing. A TFT of any known structure can be employed as the drivingTFT 1601.

Formed next is a transparent conductive film, typically an ITO film,which is then patterned into a desired shape to obtain a pixel electrode1608. The pixel electrode 1608 here serves as an anode. Contact holesreaching the source region and drain region, namely 1604 a and 1604 c,of the driving TFT are formed in the interlayer film 1606. A laminateconsisting of a Ti layer, an Al layer that contains Ti, and another Tilayer is formed and patterned into a desired shape to obtain wiringlines 1607 and 1609. The TFT is made conductive by contacting the wiringline 1609 to the pixel electrode 1608.

Then an insulating film is formed from an organic resin material such asacrylic. An opening is formed in the insulating film at a position thatcoincides with the position of the pixel electrode 1608 of an OLEDelement 1614 to obtain an insulating film 1610. The opening has to beformed to have side walls tapered gently enough to avoid degradation ordiscontinuation of the OLED layer due to the level difference in sidewalls of the opening.

An OLED layer 1611 is formed next. Thereafter, an opposite electrode(cathode) 1612 of the OLED element 1614 is formed from a laminateconsisting of a cesium (Cs) film 2 nm or less in thickness and a silver(Ag) film 10 nm or less in thickness which are layered in order. If theopposite electrode 1612 of the OLED element 1614 is very thin, lightgenerated in the OLED layer 1611 is transmitted through the oppositeelectrode 1612 and emitted in the direction opposite to the pixelsubstrate 1600. Next, a protective film 1613 is formed in order toprotect the OLED element 1614.

In the display device that emits light in the direction opposite to thepixel substrate 1600, light emission of the OLED element 1614 does notneed to travel through the components formed on the pixel substrate 1600side, including the driving TFT 1601, to be viewed. Therefore this typeof display devices can have a large aperture ratio.

The pixel electrode 1608 may serve as a cathode while the oppositeelectrode 1612 serves as an anode if TiN or the like is used to form thepixel electrode and a transparent conductive film such as an ITO film isused for the opposite electrode. Then light generated in the OLED layer1611 can be emitted in the direction opposite to the pixel substrate1600 from the anode side.

FIG. 16B is a sectional view showing the structure of a pixel that hasan OLED element structured differently from FIG. 16A.

Components in FIG. 16B that are identical with those in FIG. 16A aredenoted by the same reference symbols in the explanation.

The pixel of FIG. 16B is formed by a process identical with the processfor the pixel of FIG. 16A up through formation of the driving TFT 1601and interlayer film 1606.

Next, contact holes reaching the source region and drain region, 1604 aand 1604 c, of the driving TFT are formed in the interlayer film 1606.Thereafter, a laminate consisting of a Ti layer, an Al layer thatcontains Ti, and another Ti layer is formed and a transparent conductivefilm, typically an ITO film, is formed in succession. The laminateconsisting of a Ti layer, an Al layer that contains Ti, and another Tilayer and the transparent conductive film, typically an ITO film, arepatterned into desired shapes to obtain wiring lines 1621 and 1619 and apixel electrode 1620. The wiring line 1621 is composed of 1617 and 1618.The pixel electrode 1620 serves as an anode of an OLED element 1624.

Then an insulating film is formed from an organic resin material such asacrylic. An opening is formed in the insulating film at a position thatcoincides with the position of the pixel electrode 1620 of the OLEDelement 1624 to obtain the insulating film 1610. The opening has to beformed to have side walls tapered gently enough to avoid degradation ordiscontinuation of the OLED layer due to the level difference in sidewalls of the opening.

The OLED layer 1611 is formed next. Thereafter, an opposite electrode(cathode) 1612 of the OLED element 1624 is formed from a laminateconsisting of a cesium (Cs) film 2 nm or less in thickness and a silver(Ag) film 10 nm or less in thickness which are layered in order. If theopposite electrode 1612 of the OLED element 1624 is very thin, lightgenerated in the OLED layer 1611 is transmitted through the oppositeelectrode 1612 and emitted in the direction opposite to the pixelsubstrate 1600. Next, the protective film 1613 is formed in order toprotect the OLED element 1624.

In the display device that emits light in the direction opposite to thepixel substrate 1600, light emission of the OLED element 1624 does notneed to travel through the components formed on the pixel substrate 1600side, including the driving TFT 1601, to be viewed. Therefore this typeof display devices can have a large aperture ratio.

The pixel electrode 1620 and the wiring line 1621 may serve as a cathodewhile the opposite electrode 1612 serves as an anode if TiN or the likeis used to form the pixel electrode and a transparent conductive filmsuch as an ITO film is used for the opposite electrode. Then lightgenerated in the OLED layer 1611 can be emitted in the directionopposite to the pixel substrate 1600 from the anode side.

Compared to the pixel structured as shown in FIG. 16A, the pixelstructured as shown in FIG. 16B can reduce the number of photo masksrequired in the manufacturing process and can simplify the processbecause the wiring line 1619, which is connected to the source region ordrain region of the driving TFT, and the pixel electrode 1620 can bepatterned by using the same photo mask.

This embodiment may be combined freely with Embodiments 1 through 4.

Embodiment 6

The display device of the present invention can be used to electronicapparatuses.

An example of the electronic apparatuses using the display device of thepresent invention is shown in FIGS. 14A and 14B.

FIG. 14A shows a portable information terminal which is comprised of amain body 1400, a display portion 1401, a power supply switch 1402, anoperation key 1403, an exterior connection port 1404, an audio outputportion 1405, an audio input portion 1406, a camera portion 1407, andthe like. The display device of the present invention can be used to thedisplay portion 1401. As a result, as shown in FIG. 14A, the width W1 ofthe frame around the display screen that has the display portion 1401can be lessened, therefore, the width W2 of the main body of theportable information terminal device can be lessened.

Thus, a portable information device convenient to carry is provided.

FIG. 14B shows a cellular phone which is comprised of a main body 1410,a display portion 1411, a power supply switch 1412, an operation key1413, an exterior input port 1414, an audio output portion 1415, anaudio input 1416, an antenna 1417, and the like. The display device ofthe present invention can be used to the display portion 1411. As aresult, as shown in FIG. 14B, the width W3 of the frame around thedisplay screen that has the display portion can be lessened, therefore,the width W4 of the main body of the cellular phone can be lessened.

Thus, the cellular phone convenient to carry is provided.

The display device is not limited to the above examples, it also can beused to various electronic apparatuses.

This embodiment may be combined freely with Embodiments 1 through 4.

According to the present invention, a gate signal line driving circuitis arranged in parallel to a source signal line driving circuit in adisplay device with the driving circuits (source signal line drivingcircuit and gate signal line driving circuit) for inputting signals to aplurality of pixels being formed on the same insulating surface wherethe plural pixels are formed as in the above-described structures. Theframe area in the lateral direction of the display device can be thusreduced.

1. A display device comprising: a pixel portion over a first substrate,comprising: a plurality of gate signal lines and a plurality of sourcesignal lines arranged in a matrix; a plurality of lines arranged inparallel with the plurality of gate signal lines; and a plurality ofpixels each comprising a thin film transistor; a gate driver over thefirst substrate and electrically connected to the plurality of gatesignal lines; and a source driver over the first substrate andelectrically connected to the plurality of source signal lines; and asealing member bonding the first substrate and a second substrate overat least one of the plurality of gate signal lines with an interlayerfilm therebetween, wherein each of the plurality of pixels iselectrically connected to a corresponding one of the plurality of gatesignal lines, to a corresponding one of the plurality of source signallines, and to a corresponding one of the plurality of lines, wherein thegate driver and the source driver are arranged in one direction chosenout of four directions which are above, below, left and right, withrespect to the pixel portion, and wherein the plurality of gate signallines turn orthogonally.
 2. The display device according to claim 1,wherein the display device is a liquid crystal display device.
 3. Thedisplay device according to claim 1, wherein the display device is anorganic light emitting diode display device.
 4. The display deviceaccording to claim 1, wherein the display device is used to a portableinformation terminal.
 5. The display device according to claim 1,wherein the display device is used to a cellular phone.
 6. A displaydevice comprising: a pixel portion over a first substrate, comprising: aplurality of gate signal lines and a plurality of source signal linesarranged in a matrix; a plurality of lines arranged in parallel with theplurality of gate signal lines; and a plurality of pixels eachcomprising a thin film transistor; a gate driver over the firstsubstrate and electrically connected to the plurality of gate signallines; and a source driver over the first substrate and electricallyconnected to the plurality of source signal lines; and a sealing memberbonding the first substrate and a second substrate over at least one ofthe plurality of gate signal lines with an interlayer film therebetween,wherein each of the plurality of pixels is electrically connected to acorresponding one of the plurality of gate signal lines, to acorresponding one of the plurality of source signal lines, and to acorresponding one of the plurality of lines, wherein the gate driver andthe source driver are arranged in one direction chosen out of fourdirections which are above, below, left and right, with respect to thepixel portion wherein the plurality of gate signal lines turnorthogonally, and wherein output signals of the gate driver are input tothe plurality of gate signal lines in the pixel portion from left andright of the pixel portion.
 7. The display device according to claim 6,wherein the display device is a liquid crystal display device.
 8. Thedisplay device according to claim 6, wherein the display device is anorganic light emitting diode display device.
 9. The display deviceaccording to claim 6, wherein the display device is used to a portableinformation terminal.
 10. The display device according to claim 6,wherein the display device is used to a cellular phone.
 11. A displaydevice comprising: a pixel portion over a first substrate, comprising: aplurality of gate signal lines and a plurality of source signal linesarranged in a matrix; a plurality of lines arranged in parallel with theplurality of gate signal lines; and a plurality of pixels eachcomprising a thin film transistor, wherein one of a source region and adrain region of the thin film transistor is connected to one of theplurality of the source signal lines and the other is connected to acapacitor storage; a gate driver over the first substrate andelectrically connected to the plurality of gate signal lines; and asource driver over the first substrate and electrically connected to theplurality of source signal lines; and a sealing member bonding the firstsubstrate and a second substrate over at least one of the plurality ofgate signal lines with an interlayer film therebetween, wherein each ofthe plurality of pixels is electrically connected to a corresponding oneof the plurality of gate signal lines, to a corresponding one of theplurality of source signal lines, and to a corresponding one of theplurality of lines, wherein the gate driver and the source driver arearranged in one direction chosen out of four directions which are above,below, left and right, with respect to the pixel portion, and whereinthe plurality of gate signal lines turn orthogonally.
 12. The displaydevice according to claim 11, wherein the display device is a liquidcrystal display device.
 13. The display device according to claim 11,wherein the display device is an organic light emitting diode displaydevice.
 14. The display device according to claim 11, wherein thedisplay device is used to a portable information terminal.
 15. Thedisplay device according to claim 11, wherein the display device is usedto a cellular phone.
 16. A display device comprising: a pixel portionover a first substrate, comprising: a plurality of gate signal lines anda plurality of source signal lines arranged in a matrix; a plurality oflines arranged in parallel with the plurality of gate signal lines; anda plurality of pixels each comprising a thin film transistor, whereinone of a source region and a drain region of the thin film transistor isconnected to one of the plurality of the source signal lines and theother is connected to a capacitor storage; a gate driver over the firstsubstrate and electrically connected to the plurality of gate signallines; and a source driver over the first substrate and electricallyconnected to the plurality of source signal lines; and a sealing memberbonding the first substrate and a second substrate over at least one ofthe plurality of gate signal lines with an interlayer film therebetween,wherein each of the plurality of pixels is electrically connected to acorresponding one of the plurality of gate signal lines, to acorresponding one of the plurality of source signal lines, and to acorresponding one of the plurality of lines, wherein the gate driver andthe source driver are arranged in one direction chosen out of fourdirections which are above, below, left and right, with respect to thepixel portion, wherein the plurality of gate signal lines turnorthogonally, and wherein output signals of the gate driver are input tothe plurality of gate signal lines in the pixel portion from left andright of the pixel portion.
 17. The display device according to claim16, wherein the display device is a liquid crystal display device. 18.The display device according to claim 16, wherein the display device isan organic light emitting diode display device.
 19. The display deviceaccording to claim 16, wherein the display device is used to a portableinformation terminal.
 20. The display device according to claim 16,wherein the display device is used to a cellular phone.